Sensors for dynamically detecting substrate breakage and misalignment of a moving substrate

ABSTRACT

An apparatus and method incorporating at least two sensors that detect the presence of a substrate is provided. In one embodiment, a method for transferring a substrate in a processing system is described. The method includes positioning a substrate on an end effector in a first chamber, moving the substrate through an opening between the first chamber and a second chamber along a substrate travel path, and sensing opposing sides of the substrate travel path using at least two sensors positioned proximate to the opening, each of the at least two sensors defining a beam path that is directed through opposing edge regions of the substrate when at least a portion of an edge region traverses the beam path.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.10/973,116, which was filed Oct. 26, 2004, and issued as U.S. Pat. No.7,440,091 on Oct. 21, 2008, which is incorporated by reference in itsentirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the present invention generally relate to an apparatusand method for detecting substrate breakage and misalignment of a movingsubstrate in a continuous and cost-effective manner.

2. Description of the Related Art

Substrate processing systems are used to process substrates such assilicon wafers in the production of integrated circuit devices and glasspanels in the manufacture of flat panel displays. Typically, one or morerobots are disposed in the substrate processing system to transfersubstrates through a plurality of process chambers for conducting asequence of processing steps of the fabrication process. Generally, asubstrate processing system includes a cluster tool having a centrallylocated transfer chamber, with a transfer chamber robot disposedtherein, and a plurality of process chambers surrounding the transferchamber. The transfer chamber is sometimes coupled to a factoryinterface that houses a factory interface robot and a plurality ofsubstrate cassettes, each of which holds a plurality of substrates. Tofacilitate substrate transfer between a generally ambient environmentwithin the factory interface and a vacuum environment within thetransfer chamber, a load lock chamber which may be pumped down to createa vacuum therein, and vented to provide an ambient condition therein, isdisposed between the factory interface and the transfer chamber. The useof robots in the processing of substrates is essential to processing alarge number of substrates through many different types of processingtechnologies with minimal contamination (e.g., substrate handlingcontamination), high speed, and accuracy to minimize defects and providea high throughput system.

In operation, the factory interface robot transfers one or moresubstrates from a cassette to the interior of the load lock chamber. Theload lock chamber is pumped down to create a vacuum therein, and thenthe transfer chamber robot transfers the substrate(s) from the load lockto the interior of one or more of the process chambers. After thesubstrate processing sequence is completed, the transfer chamber robotreturns the processed substrate to the load lock, the load lock is thenvented and the factory interface robot transfers the processed substrateto a cassette for subsequent removal from the processing system. Suchsubstrate processing systems are available from AKT, Inc., awholly-owned subsidiary of Applied Materials, Inc., of Santa Clara,Calif.

The trend towards increasingly larger substrates and smaller devicefeatures requires increasingly precise positional accuracy of thesubstrate in the various process chambers in order to ensure repetitivedevice fabrication with low defect rates. Increasing the positionalaccuracy of substrates throughout the processing system is a challenge.In one example, flat-panel display substrates (e.g., glass substrates)are transferred on an end effector (e.g., a blade or fingers) of a robotto and from the various chambers of the processing system. It isdifficult to ensure that flat-panel display substrates align properlywith the end effectors of the robots, and once aligned, that thesubstrate can pass through slots or other obstacles in the load lock orprocess chambers without collisions due to a shift in alignment (i.e.,misalignment) during transfer. A collision may not only chip or crackthe flat-panel display substrate, but also create and deposit debris inthe load lock or process chambers. Creating such debris may result inprocessing defects or other damage to the display or subsequentlyprocessed displays. Thus, the presence of debris often requires shuttingdown the system, or a portion thereof, to thoroughly remove thepotentially contaminating debris. Moreover, with larger dimensionsubstrates and increased device density, the value of each substrate hasgreatly increased.

Accordingly, damage to the substrate or yield loss because of substratemisalignment is highly undesirable due to consequential increase in costand reduction in throughput.

A number of strategies have been employed in order to enhance thepositional accuracy (i.e., alignment) of substrates throughout theprocessing system. For example, a transfer chamber may be equipped withgroups of four sensors adjacent the entry of each load lock and processchamber in a sensor arrangement such that the sensors may simultaneouslydetect the presence of the four corners of a rectangular glass panel forsensing its alignment prior to the robot transferring the substrate intothe chamber. Thus, the four sensors are arranged in the base of thetransfer chamber at spaced-apart locations such that all four sensorsare simultaneously positioned below the four corners of the stationarysubstrate. Such a disperse arrangement of sensors in front of each ofthe chambers requires a large number of sensors positioned at manylocations across the base of the transfer chamber. Various arrangementsof sensors disposed across the base of the transfer chamber have beenproposed.

Although conventional sensor arrangements perform satisfactorily, inoperation there are several inherent limitations associated withproviding these arrangements of sensors. In practice, because thesensors detect the alignment of a single substrate at a time, thetransfer chamber may handle/manage only one substrate at a time due tothe disperse arrangement of sensors across the base of the transferchamber. Thus the transfer chamber robot is effectively limited to asingle-arm robot which results in reduced throughput of the processingsystem. Another limitation, which also contributes to a reducedthroughput of the processing system, is that the substrate is stationarywhen positioned over the four sensors during the sensing of itsalignment. Still another limitation is at least four sensors arerequired to sense the alignment of a single substrate. Finally, anotherlimitation is that the four sensors detect substrate defects (e.g., asubstrate chip) only at the corners of the substrate.

With the apparatus and method of the present invention, the relativelysimple arrangement and fewer number of sensors required to detect themisalignment and/or breakage of a substrate make the present inventioneasy to implement with relatively low cost.

SUMMARY OF THE INVENTION

The present invention generally provides an apparatus and methodincorporating at least two sensors that detect the presence of asubstrate. In some embodiments, the apparatus and method includesdetecting substrate defects, such as breakage or misalignment, of amoving substrate. In one embodiment, a method for sensing the presenceof a moving substrate is described. The method includes moving asubstrate relative to a first sensor and a second sensor, and sensing aplurality of first edge portions of the substrate with the first sensorand a plurality of second edge portions of the substrate with the secondsensor, the second edge portions being opposite the first edge portions.

In another embodiment, a method for transferring a substrate in aprocessing system is described. The method includes positioning asubstrate on an end effector in a first chamber, moving the substratethrough an opening between the first chamber and a second chamber alonga substrate travel path, and sensing opposing sides of the substratetravel path using at least two sensors positioned proximate to theopening, each of the at least two sensors defining a beam path that isdirected through opposing edge regions of the substrate when at least aportion of an edge region traverses the beam path.

In another embodiment, a method for transferring a substrate in aprocessing system is described. The method includes positioning asubstrate on an end effector in a transfer chamber, moving the substratethrough an opening in the transfer chamber along a substrate travelpath, sensing opposing sides of the substrate travel path using at leasttwo sensors positioned proximate to the opening, each of the at leasttwo sensors defining a beam path that is directed through the substratewhen the substrate traverses the beam path, and detecting the presenceof at least one parallel edge region of the substrate as the substrateis moved along the substrate travel path.

In another embodiment, a substrate processing system having an endeffector disposed in a first chamber, at least a first sensor and asecond sensor, and a controller configured to perform a process isdescribed. The process includes moving a substrate on the end effectoralong a substrate travel path through an opening between the firstchamber and a second chamber, sensing opposing sides of the substratetravel path using the first and second sensors, each of the first andsecond sensors defining a beam path that is directed through opposingedge regions of the substrate when at least a portion of an edge regiontraverses the beam path, and monitoring a signal from each of the firstand second sensors.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentinvention can be understood in detail, a more particular description ofthe invention, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this invention and are therefore not to beconsidered limiting of its scope, for the invention may admit to otherequally effective embodiments.

FIG. 1 is a plan view of one embodiment of a processing system includingsensors arranged in accordance with one embodiment of the presentinvention;

FIG. 2 is an enlarged partial sectional view of the processing systemdepicting a sensor arrangement in proximity to the entry/exit port of aprocess chamber for detecting substrate breakage and misalignment beforeand after processing within the chamber;

FIGS. 3A and 3B are enlarged partial sectional views of the processingsystem along line 3-3 of FIG. 1 depicting a sensor arrangement within anambient environment of a factory interface, wherein FIG. 3A shows thesensor arrangement in proximity to a three-slot load lock chamber fordetecting substrate breakage and misalignment of substrates transferredinto and out of the three slots, and FIG. 3B shows the sensorarrangement in proximity to a four-slot load lock chamber;

FIGS. 4A through 4E are top views of a substrate moving over two sensorsand the corresponding sensor signals, wherein FIG. 4A depicts a properlyaligned, defect-free substrate, FIGS. 4B and 4D depict a chippedsubstrate, FIG. 4C depicts a cracked substrate, and FIG. 4E depicts amisaligned substrate; and

FIG. 5 is a top view of a substrate being transferred on the blade of afactory interface robot under two sensors mounted on the exterior of aload lock chamber and the corresponding sensor signals.

DETAILED DESCRIPTION

The present invention generally provides an apparatus and methodincorporating at least two sensors that continuously detect the presenceof a substrate chip, crack, and/or misalignment along two parallel edgesof a moving substrate. FIG. 1 is a plan view of one embodiment of aprocessing system 100 suitable for processing large area substrates 106(e.g., glass or polymer substrates) having a top surface area of greaterthan about 25,000 cm², for example, a glass substrate having a topsurface area of about 40,000 cm² (2.2 m×1.9 m). The processing system100 typically includes a factory interface 110 coupled to a transferchamber 120 by at least one load lock chamber 160. As depicted in FIG.1, the load lock chamber 160 is disposed between the factory interface110 and the transfer chamber 120 to facilitate substrate transferbetween a substantially ambient environment maintained in the factoryinterface 110 and a vacuum environment maintained in the transferchamber 120.

The factory interface 110 generally includes a plurality of substratestorage cassettes 112 and at least one atmospheric robot 114 (previouslyreferred to as the factory interface robot). The cassettes 112, each ofwhich hold a plurality of substrates, are removably disposed in aplurality of bays 116 formed on typically one side of the factoryinterface 110. The atmospheric robot 114 is adapted to transfersubstrates 106 between the cassettes 112 and the load lock chamber 160.Typically, the factory interface 110 is maintained at or slightly aboveatmospheric pressure. Filtered air is normally supplied to the interiorof the factory interface 110 to minimize the concentration of particleswithin the factory interface that could lead to particulatecontamination of substrate surfaces.

The transfer chamber 120 having a base 122, sidewalls 124, and a top lid126 (not shown in FIG. 1) houses at least one vacuum robot 130(previously referred to as the transfer chamber robot) generallydisposed on the base 122 of the transfer chamber 120. The transferchamber 120 defines an evacuable interior volume through which thevacuum robot 130 transfers substrates 106 prior to processing in aprocess chamber 150 or delivery to the load lock chamber 160. Thesidewalls 124 include an opening or port (not shown), adjacent each ofthe process chambers 150 and load lock chamber 160, through which thesubstrate 106 may be transferred by the vacuum robot 130 to the interiorof each of the chambers 150, 160. Typically, the transfer chamber 120 ismaintained at a vacuum condition similar to the sub-atmosphericconditions within the process chambers 150 in order to minimize oreliminate the necessity of adjusting the pressure within the transferchamber 120 and the pressure within the individual process chambers 150after each substrate transfer therebetween. The interior of each processchamber 150 is selectively isolated from the interior of the transferchamber 120 through the use of a slit valve (not shown) to selectivelyseal the port in the sidewall 124 of the transfer chamber 120 adjacenteach of the process chambers 150.

The process chambers 150 are typically bolted to the exterior of thetransfer chamber 120. Different process chambers 150 may be attached tothe transfer chamber 120 to permit processing a substrate through aprocessing sequence necessary to form a predefined structure or featureupon the substrate surface. Examples of suitable process chambers 150include chemical vapor deposition (CVD) chambers, physical vapordeposition (PVD) chambers, ion implantation chambers, etch chambers,orientation chambers, planarization chambers, lithography chambers, aswell as other chambers used in processing a substrate. Optionally, oneof the process chambers 150 may be a pre-heat chamber that thermallyconditions substrates prior to processing in order to enhance throughputof the system 100.

The load lock chamber 160 facilitates transfer of the substrates betweenthe vacuum environment of the transfer chamber 120 and the substantiallyambient environment of the factory interface 110 without loss of vacuumwithin the transfer chamber 120. In a sidewall of the load lock chamber160 adjacent the factory interface 110, the load lock chamber 160 hasone or more entry/exit slots (not shown) through which the atmosphericrobot 114 may transfer substrates 106 into and out of the load lockchamber 160. Likewise, the load lock chamber 160 has the same number ofentry/exit slots in the opposite sidewall of the load lock chamber 160through which the vacuum robot 130 may transfer substrates 106 betweenthe interiors of the load lock chamber 160 and the transfer chamber 120.Each of the entry/exit slots of the load lock chamber 160 is selectivelysealed by a slit valve (not shown) to isolate the interior of the loadlock chamber 160 from the interiors of the factory interface 110 and thetransfer chamber 120.

The atmospheric robot 114 and the vacuum robot 130 are equipped with endeffectors, such as a blade 118 or fingers 136, respectively, fordirectly supporting a substrate 106 during transfer. Each of the robots114, 130 may have one or more end effectors, each coupled to anindependently controllable motor (e.g. a dual-arm robot) or, forexample, have two end effectors coupled to the robot 114, 130 through acommon linkage. As depicted in FIG. 1, vacuum robot 130 is a dual-armrobot having a first arm 132 connected to an upper end effector 134having fingers 136 for supporting a substrate 106 (designated by thedashed lines) thereon, and a second arm 138 connected to a lower endeffector (not shown) with fingers for supporting and moving anothersubstrate within the transfer chamber 120. For increased throughput, thedual-arm vacuum robot 130 may simultaneously transfer two substratesinto and out of the various process chambers 150 and to/from the loadlock chamber 160. For increased throughput, preferably each of therobots 114, 130 is equipped with two end effectors.

The base 122 of the transfer chamber 120 includes a plurality of viewwindows 128 disposed proximate the port adjacent each of the processchambers 150 and load lock chamber 160. Proximate each port, at leasttwo sensors 140A, 140B are mounted on or near the exteriors of twowindows 128 such that each of the at least two sensors 140A, 140B mayview (i.e., sense) an edge portion of the substrate 106 prior to passingthrough the port. Preferably the sensors 140A, 140B are disposed on theexterior of the windows 128 (i.e., exterior of the transfer chamber) sothat the sensors 140A, 140B are isolated from the environment andpotentially moderate to high temperatures within the transfer chamber120. The window 128 may be fabricated of quartz or other material (e.g.,glass, plastic) that does not substantially interfere with the detectionmechanism of the sensor, for example, a beam of light emitted andreflected back to the sensor 140A (or 140B) through the window 128.

FIG. 2 is an enlarged partial sectional side view of the transferchamber 120, depicting an arrangement of any one of the sensors 140A,140B disposed proximate the entry/exit port (not shown) in sidewall 124of the transfer chamber 120 adjacent each of the process chambers 150and load lock chamber 160. Referring to one of the sensors, for examplesensor 140A proximate one of the process chambers 150 of FIG. 1, thesensor 140A includes a transmitter 144 and a receiver 148 generallypositioned on or near the exterior of the window 128. The correspondingreflector 142A is mounted on or near an interior side of the transferchamber lid 126. Because the reflector 142A is essentially a mirror-typedevice, it is typically less sensitive to temperature and may beoperational within a vacuum and moderate temperature environment of thetransfer chamber 120. During sensing operation, a beam of light emittedby the transmitter 144 travels through the window 128 along a beam path146 to the reflector 142A and is reflected by the reflector 142A alonganother beam path 147 back through the window 128 to the receiver 148.When a glass substrate crosses beam paths 146, 147, the intensity of thebeam received by the receiver 148 is attenuated, due to loss of signalfrom the beam reflections at each glass/air interface encountered alongpaths 146, 147, indicating the presence of the substrate 106. Sensors140A, 140B are coupled to a controller 129 configured to continuallyrecord, monitor, and compare the beam signals received by the receivers148 of sensors 140A and 140B. The controller 129 generally includes aCPU, memory and support circuits.

Numerous other sensor configurations may be used to sense the presenceof a substrate 106. For example, the reflector 142A may be mounted ontothe exterior side of another window (not shown) disposed in the top lid126 of the transfer chamber 120. Similarly, in another example, thesensor 140A may emit a beam that travels through the window 128 to asecond sensor (not shown) positioned on the exterior side of anotherwindow (not shown) disposed in the top lid 126 of the transfer chamber120. Alternatively, other positions of the sensor 140A may be utilizedincluding those within the transfer chamber 120 as long as theenvironment within the chamber 120 to which the sensor is exposed lieswithin the operational range (e.g., thermal operating range) of theparticular sensor.

Sensor 140A or 140B may include separate emitting and receiving units ormay be self-contained such as “thru-beam” and “reflective” sensors orother type of sensing mechanism suitable for detecting the presence ofthe substrate. In at least one embodiment of the invention, a filter orsimilar mechanism may be employed to block thermal energy (e.g.,infrared wavelengths) from reaching/heating the reflector 142A when, forexample, a heated substrate is transferred within the transfer chamber120, as such heating may affect the reflective properties of certainreflectors. For example, a filter that passes the wavelength orwavelengths emitted by the transmitter 144, but that reflects infraredwavelengths, may be positioned near the reflector 142A.

In one example, the transmitter 144 and receiver 148 may be an Omron®Model No. E32-R16 sensor head having an E3X-DA6amplifier/transmitter/receiver, which operates at 660 nm, manufacturedby Omron® Electronics LLC, of Schaumburg, Illinois. The reflector 142Amay be, for example, a Balluff Model No. BOS R-14 reflector manufacturedby Balluff, Inc., of Florence, Ky., or an Omron® Model No. E39-R1reflector. The Omron® E32-R16 sensor has a light emitting diode (LED)that may be used to detect a substrate defect (i.e., breakage ormisalignment) having a dimension greater than or equal to about 4inches. In another example, the transmitter 144 and receiver 148 may bean Omron® Model No. E3C-LR11 laser sensor head operating with amplifiersModel Nos. E3C-LDA11, E3C-LDA21, and a reflector Model No. E39-R12. TheOmron® E3C-LR11 laser sensor head may be used to detect substratedefects having a dimension greater than or equal to about 1 mm. Othersensors, reflectors, amplifiers, transmitters, receivers, wavelengths,etc., may be employed. In addition, other sensors having a differentsensing mechanism, for example, ultrasonic, may be utilized.

Referring back to FIG. 1, the load lock chamber 160 is also equippedwith at least two sensors 140A, 140B proximate the entry/exit slots (notshown) of the load lock adjacent the factory interface 110. The loadlock chamber 160 preferably includes one or more vertically-stacked,environmentally-isolatable substrate transfer chambers that may beindividually pumped down to hold a vacuum and vented to contain anambient condition therein. Each of the one or more vertically-stackedenvironmentally-isolatable chambers has one or more entry/exit slots toallow passage of the substrate therethrough. The arrangement of thesesensors 140A, 140B allows detection of substrate breakage and/orsubstrate misalignment prior to the substrate 106 entering the load lockchamber 160 for subsequent transfer to the transfer chamber 120 andprocessing. Sensors 140A and 140B are mounted in a spaced-apartrelationship such that each of the beams emitted from sensors 140A, 140Bpass through a substrate near its parallel edges as the substrate passesthe sensors during substrate transfer into or out of a slot of the loadlock chamber 160. This spaced-apart sensor arrangement is applicable toany size load lock chamber 160 having any number of slots.

FIGS. 3A and 3B illustrate enlarged sectional side views of thearrangement of the sensors 140A, 140B along line 3-3 of FIG. 1. Each ofthe sensors 140A, 140B and corresponding reflectors 142A, 142B isgenerally mounted to the exteriors 162, 172 of the load lock chambers160, 170, using a fastener such as a bracket (e.g., sensor bracket 540and reflector bracket 542 as illustrated in FIG. 5) or frame to securethe sensor/reflector in a fixed position. In one example, shown in FIG.3A, sensors 140A, 140B are mounted above three slots 164, 166, 168 ofthe load lock chamber 160 and corresponding reflectors 142A, 142B aremounted below the three slots. The load lock chamber 160 having threeslots can include one or more environmentally-isolatable chambers suchas a triple single-slot load lock chamber (shown in FIG. 3A), a singletriple-slot load lock chamber, three vertically stacked load lockchambers each having a single slot, or any other combination of loadlock chambers. Likewise, in another example, FIG. 3B illustrates a sideview of an arrangement of sensors 140A, 140B proximate a four-slot loadlock chamber 170. Sensors 140A, 140B are mounted below the four slots174, 176, 178, 180 of load lock chamber and corresponding reflectors142A, 142B are mounted above the four slots. The load lock chamber 170having four slots can include one or more environmentally-isolatablechambers such as a double dual slot load lock (DDSL) chamber, aquadruple single-slot load lock chamber, a single quadruple-slot loadlock chamber, four vertically stacked load lock chambers each having asingle slot, or any other combination of load lock chambers. Asillustrated in FIGS. 3A and 3B, sensors 140A, 140B may be mounted aboveor below the slots of the load lock chambers 160, 170.

In FIGS. 3A and 3B, each of the sensors 140A, 140B and correspondingreflectors 142A, 142B operate together as described in FIG. 2, howeverbecause no environmental provisions need to be made on the factoryinterface side it is unnecessary to have a view window forenvironmentally isolating the sensor As such, the beam of light emittedby the transmitter of sensor 140A (or 140B) travels along a path(indicated by the dashed line) to corresponding reflector 142A (or 142B)and is reflected by the reflector 142A along another path (alsoindicated by the dashed line; the lateral separation of the paths is notdiscernible in this view) to the receiver of sensor 140A (or 140B).

In operation, substrate breakage and substrate alignment may be detectedwhen a substrate 106 passes through the beams of light emitted by a pairof sensors 140A, 140B disposed in the transfer chamber 120 proximate theport adjacent one of the process chambers 150 or load lock chamber 160,as illustrated in FIGS. 4A through 4E. The dashed lines near the edgesof the substrate 106 indicate the paths near the edges of the substratewhere the traveling glass substrate crosses the beams emitted by sensors140A, 140B located below the substrate.

FIG. 4A illustrates a top view of a defect-free (i.e., no chips orcracks) substrate 106 being transferred on an end effector 134 withproper alignment. Prior to sensing the substrate 400A, 400B, thereceivers 148 of each of the sensors 140A, 140B detect full beam signals401A, 401B reflected from the corresponding reflectors 142A, 142B (notshown) located above the substrate. When the substrate 106 enters (i.e.,breaks) the beam paths at points 402A, 402B, the beam signals 403A, 403Breceived by the receivers 148 decrease, due to signal loss at theglass/air interfaces of the substrate 106, indicating the presence ofthe substrate 106. The beam signals 405A, 405B remain low as thesubstrate 106 continues to traverse the beams (as indicated by thedashed lines) along the length of the substrate 106. Just as the ends ofthe substrate 406A, 406B travel past the beams, the beam signals 407A,407B increase back to their original uninterrupted full beam signals409A, 409B. Likewise, when a defect-free substrate is transferred backout of the processing chamber 150 (or load lock chamber 160) on an endeffector with proper alignment, a similar signal is obtained as thesubstrate first enters the path of the beams at points 406A, 406B andexits the beams at points 402A, 402B, i.e., in reverse order of theprevious description.

Referring to FIGS. 4B, 4C, and 4D, substrate breakage may be detectedwhen a substrate 106 passes through the beams of light emitted by a pairof sensors 140A, 140B. FIG. 4B illustrates a top view of a substrate106, having an edge chip near one edge of the substrate, beingtransferred on an end effector 134 with proper alignment. Prior tosensing the substrate 400A, 400B, the receivers 148 of each of thesensors 140A, 140B detect full beam signals 401A, 401B. When thesubstrate enters the beam paths at points 402A, 402B, the beam signals403A, 403B received by the receivers 148 decrease, indicating thepresence of the substrate 106. The beam signals 405A, 405B remain low asthe substrate continues to traverse the beams (as indicated by thedashed lines) along the length of the substrate. However, when thebeginning of the substrate chip 410B enters the beam path, the signalincreases back to an uninterrupted full beam signal 411B and continuesto detect the absence of the substrate 413B over the length of the chip412B. As the end of the substrate chip 414B passes through the beam, thebeam signal 415B decreases again indicating the presence of thesubstrate 405B until the end of the substrate 406B passes through thebeam.

FIG. 4C illustrates a top view of a substrate 106, having a crack nearone edge of the substrate, being transferred on an end effector 134 withproper alignment. Prior to sensing the substrate, the receivers 148 ofeach of the sensors 140A, 140B detect full beam signals 401A, 401B. Whenthe substrate enters the beam paths at points 402A, 402B, the beamsignals 403A, 403B received by the receivers 148 decrease, indicatingthe presence of the substrate 106. The beam signals 405A, 405B remainlow as the substrate continues to traverse the beams along the length ofthe substrate. However, when the beginning of the substrate crack 420Benters the beam path, the signal increases back to an uninterrupted fullbeam signal 421B and continues to detect the absence of the substrate423B over the length of the crack 422B. As the end of the substratecrack 424B passes through the beam, the beam signal 425B decreases againindicating the presence of the substrate 405B until the end of thesubstrate 406B passes through the beam.

FIG. 4D illustrates a top view of a substrate 106, having a corner edgechip near one edge of the substrate, being transferred on an endeffector 134 with proper alignment. Prior to sensing the substrate 400A,400B, the receivers 148 of each of the sensors 140A, 140B detect fullbeam signals 401A, 429B reflected from the corresponding reflectors142A, 142B (not shown) located above the substrate. When the substrateenters the beam path of sensor 140A at point 402A, the beam signal 403Adecreases indicating the presence of the substrate 106, however,concurrently, the beam path of sensor 140B at point 430B remainsuninterrupted due to the presence of the corner chip and the signal 429Bremains high. An uninterrupted full signal 429B continues while the beamfrom sensor 140B traverses the length 432B of the corner chip. Uponreaching the end of the chip 434B, the signal decreases at point 435Bindicating the presence of the substrate 437B until the end of thesubstrate 406B passes through the beam. Due to the substrate chip,sensor 140B detects a shorter length substrate 437B as compared to thelength of the substrate 405A sensed by sensor 140A. The length of thesubstrate, as detected by sensor 140B, is shortened by distance 432Bwhich results in a delay 433B before the substrate 106 is detected atpoint 435B.

FIG. 4E illustrates a top view of a substrate 106 being transferred onan end effector 134 with a misalignment. Prior to sensing the substrate442A, 442B, the receivers 148 of each of the sensors 140A, 140B detectfull beam signals 443A, 443B reflected from the corresponding reflectors142A, 142B (not shown) located above the substrate. When the substrateenters the beam path of sensor 140A at point 444A, the beam signal 445Areceived by the corresponding receiver 148 decreases indicating thepresence of the substrate 106, however, concurrently, the beam path ofsensor 140B remains uninterrupted for an additional length 444B due tothe shift in alignment (i.e., misalignment). The uninterrupted fullsignal 443B continues while the beam traverses the length of themisalignment 444B. When the substrate breaks the beam path of sensor140B at point 446B, the signal 447B decreases indicating the presence ofthe substrate 106. Afterwards, at point 448A, the beam path of sensor140A detects the end of the substrate and the corresponding receiver 148increases to full strength 449A, whereas the beam path of sensor 140Bcontinues to detect the presence of the substrate until the end of thesubstrate at 450B where the signal 451B increases back to its originaluninterrupted full beam signal 453B. Due to the misalignment, bothsensors 140A and 140B detect a shorter length substrate 447A, 449B. Thelength of the substrate as detected by sensor 140A is shortened bydistance 450A which results in an early increase in signal at point 449Aas compared to a properly aligned substrate. Likewise, the length of thesubstrate 106 as detected by sensor 140B is shortened by distance 444Bwhich results in a delay before the substrate is detected at point 447B.

The sensor arrangement of the present invention advantageously allowsdetection of breakage (e.g., chip, crack) and misalignment of asubstrate while the substrate is supported and transferred on a dual-armrobot. The use of a dual-arm robot provides increased throughput of theprocessing system. Another advantage, which contributes to an increasedthroughput, is the ability to detect misalignment and breakage of asubstrate while it is moving, even at high transfer speeds (e.g., 1000mm/s) on an end effector of a robot. Still another advantage of thepresent invention is that as few as two sensors are required to detectbreakage and misalignment of a substrate. Finally, another advantage ofthe present invention is the ability to detect misalignment and breakageof a substrate along the entire length of a substrate as the substratemoves past the sensors. Furthermore, detection of substrate misalignmentand breakage may be performed during normal robotic transfer operations(i.e., in-situ), which obviates the need for additional or unnecessaryrobotic movements (including stops and starts to provide a stationarysubstrate) for the purpose of sensing a substrate.

One advantage of the present invention is substrate breakage andmisalignment may be detected as a substrate is moving, even at hightransfer speeds. During sensing for defects, the substrate is preferablymoving (e.g., being transferred on an end effector of a robot) at atransfer speed in a range of about 100 mm/s to about 2000 mm/s. Thesmallest size substrate chip, crack, or the smallest degree of substratemisalignment that may be detected by an LED or laser system is dependentupon both the beam size (i.e., the spot size or diameter) of the emittedbeam when it impinges upon a top or bottom surface of the substrate, andthe transfer speed of the substrate. In general, the smaller the emittedbeam diameter, the finer or smaller the defect feature that may bedetected. For example, a suitable laser sensor may emit a laser beamhaving a diameter in a range of about 0.5 mm to about 3 mm. However, inorder to detect substrate chips or cracks having a size as small as 1 mm(i.e., greater than about 1 mm), for example, the diameter of theemitted laser beam when the beam impinges a surface of the substrate ispreferably less than about 1 mm. Thus, the substrate is positionedwithin a working distance of the particular sensor used in order toensure the impinging beam diameter on a top or bottom surface of thesubstrate is small enough to detect the smallest size substrate chip,crack or misalignment that needs to be detected.

The size of defect that may be detected by a laser system is alsoinfluenced by the transfer speed of the substrate as a result of thevibration a moving substrate invariably experiences, for example, whilebeing transferred on an end effector of a robot. Generally, the fasterthe transfer speed or velocity of the substrate, the more vibration asubstrate experiences. Vibration tends to cause the substrate edges tomove upwards and downwards. As a result, the sensor is positioned suchthat the emitted beam impinges upon the top or bottom surface of themoving substrate at a nominal distance inward from the edge of thesubstrate. Otherwise, a beam directed at the very edge of a vibratingsubstrate would invariably sense an absence of substrate each time thesubstrate edge moves in and out of the beam due to vibration. Thus, themore a substrate vibrates, the further inward from an edge of thesubstrate the incident beam is directed. For example, a laser sensorhaving an emitted beam diameter in a range of about 0.5 mm to about 3 mmand a substrate moving at a transfer speed in a range of about 100 mm/sto about 2000 mm/s, the laser beam may be directed such that theimpinging beam on the top (or bottom) surface of the substrate ispositioned at a distance in a range of about 1 mm to about 10 mm fromthe edge of the substrate.

EXAMPLES

In one example, two Omron® Model No. E3C-LR11 laser sensors having abeam diameter of less than about 0.8 mm at working distances up to about1000 mm (i.e., working distances of less than about 40 inches) is usedto sense a substrate along its two parallel edges as the substrate,supported on an end effector of a dual-arm robot, passes the sensors. Ata substrate transfer speed of about 1000 mm/s, defects having a size ofabout 3 mm or greater were detectable. The center of the impinging beamfrom each sensor was positioned at a distance of about 3 mm inward fromthe edges of the substrate. At a substrate transfer speed of about 100mm/s, defects having a size of about 1 mm or greater were detectable,and at a substrate transfer speed of about 2000 mm/s, defects having asize of about 10 mm or greater were detectable. Thus, the two impingingbeams for sensing a substrate being transferred at a speed in a range ofabout 100 mm/s to about 2000 mm/s are preferably positioned at distancesin a range of about 1 mm to about 10 mm, respectively, inward from thesubstrate edges. Using the laser to detect defect features having a sizesmaller than 3 mm may be accomplished by decreasing the velocity of thesubstrate. Decreasing the substrate velocity decreases the vibration thesubstrate experiences and as a result smaller defects may be resolved.Conversely, increasing the substrate velocity increases the vibration ofthe substrate and the larger the detectable defect.

In another example, two Omron® Model No. E32-R16 LED sensors and twoBalluff Model No. BOS R-14 reflectors are used to sense a substratealong its two edges as the substrate supported on an end effector of arobot is transferred into a three-slot load lock chamber in aconfiguration as depicted in FIG. 3A. The LED sensor mounted above thetop slot emits a beam that travels along a beam path to the reflectorpositioned within the working distance of the LED sensor. At a substratetransfer speed of about 1000 mm/s, substrate chips having a size ofabout 4 inches or greater and misalignment of greater than or equal toabout 2.6 degrees were detectable on substrates transferred into each ofthe slots.

In still another example, two Omron® Model No. E3C-LR11 laser sensorsand Omron® odel No. E39-R12 reflectors are used to sense a substratealong its two edges as the substrate supported on an end effector of arobot is transferred into a DDSL chamber in a configuration as depictedin FIG. 3B. The laser sensor mounted below the bottom slot emits a beamthat travels along a beam path past each of the four slots to areflector mounted within the working distance of the laser sensor.Substrate chips of about 3 mm or greater and substrate misalignment ofabout 0.18 degrees or greater were detectable on substrates transferredat a velocity of about 1000 mm/s into each of the four slots of the loadlock chamber.

In practice, each of the pair of sensors 140A, 140B (and correspondingreflectors) positioned near each of the entry/exit ports of the processchambers 150 and load lock chamber 160 detect substrate breakage andmisalignment before and after processing within the process chamber orpassing through the load lock chamber. Upon sensing breakage ormisalignment of a substrate, the controller coupled to the sensors maybe configured to trigger an alarm and immediately stop themotion/transfer of the defective substrate so as to allow breakage ormisalignment to be remedied by, for example, determining the cause ofthe substrate breakage or misalignment, replacing the chipped/crackedsubstrate, and correcting the alignment of the misaligned substrate.Sometimes the detection of a chipped substrate requires opening up thetransfer chamber and/or a processing chamber to thoroughly clean anypotentially contaminating debris generated by the chip. The sensorarrangement of the present invention allows for early detection ofsubstrate defects which minimizes downtime and thus increases theoverall throughput of the system 100. For example, FIG. 5 illustrates atop view of a substrate 106 having an edge chip near one edge of thesubstrate, being transferred on an end effector 118 of factory interfacerobot 114 to load lock chamber 160. The dashed lines near the edges ofthe substrate indicate the path where the traveling substrate will crossthe beams emitted by sensors 140A, 140B positioned above the substrate106 and the corresponding signals A, B, respectively. At the onset ofsensing a substrate chip at point 510A, the corresponding signal 511Aincreases and the controller immediately stops the end effector 118 fromtraveling further into the load lock chamber 160. The chipped substratemay then be evaluated to determine whether or not it is desirable tofurther process the substrate 106.

Although the illustrative detection of substrate breakage andmisalignment uses at least two sensors 140A, 140B to sense the entirelength of a substrate near its edges provides information about thelength of a chip and/or the degree of misalignment, additional sensorsmay be utilized to sense the length of an interior portion of thesubstrate 106 to provide additional information. For example, additionalsensors positioned between sensors 140A and 140B may provide additionalinformation as to the dimensions of a substrate chip (e.g. lateral depthor width of the chip) or degree of misalignment (e.g., extent of shiftin alignment). Moreover, additional pairs of sensors 140A, 140B may bepositioned at other locations throughout the processing system 100 wherethe sensors 140A, 140B may be used to sense a single substrate at anyone time. The sensors may be mounted to essentially any interior and/orexterior surfaces of the processing system over (or under) a travel pathof a moving substrate. Accordingly, there may be more than two viewwindows proximate each port of the transfer chamber 120. For example,the base 122 may have any number of view windows to accommodateadditional sensors and/or to accommodate different spaced-apartarrangements of sensors 140A, 140B for sensing different size substratesin order to direct the beams emitted from the sensors 140A, 140B suchthat they cross a passing substrate near at least two edges of thesubstrate. Alternatively, instead of using a plurality of view windows128 proximate a port adjacent a chamber, a single long view window, forexample a long rectangular-shaped window, approximating the length ofthe port may be installed in the base 122 such that a plurality ofsensors mounted near the exterior of the single long view window maysense a passing substrate. Finally, the illustrative detection ofsubstrate breakage and misalignment is described with reference to theexemplary processing system 100, however the description is one ofillustration, and accordingly, the method may be practiced whereverdetection of breakage or misalignment of a moving substrate is desired.

While the foregoing is directed to embodiments of the present invention,other and further embodiments of the invention may be devised withoutdeparting from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

1. A method for sensing the presence of a moving substrate, comprising:moving a substrate relative to a first sensor and a second sensor; andsensing a plurality of first edge portions of the substrate with thefirst sensor and a plurality of second edge portions of the substratewith the second sensor, the second edge portions being opposite thefirst edge portions.
 2. The method of claim 1, wherein each of the firstsensor and second sensor define an optical beam path.
 3. The method ofclaim 2, wherein the optical beam path impinges a top surface or abottom surface of the substrate.
 4. The method of claim 3, wherein thebeam path is substantially orthogonal to the top surface or the bottomsurface.
 5. The method of claim 3, wherein the beam path is reflectedthrough the top surface or the bottom surface.
 6. The method of claim 1,further comprising: continuously monitoring a light beam from each ofthe first sensor and the second sensor to determine an optical intensityof the beam.
 7. The method of claim 6, further comprising: detecting acrack, a chip, or a defect in the substrate by comparing the opticalintensity of one of the first sensor or second sensor, wherein theoptical intensity of one or both of the first sensor and second sensoris greater than the optical intensity of the first sensor and secondsensor in the absence of the crack, the chip, or the defect in thesubstrate.
 8. The method of claim 6, wherein the optical intensity ofone of the first sensor or second sensor is not substantially attenuatedwhen the substrate is misaligned.
 9. The method of claim 6, wherein theoptical intensity of the first sensor is attenuated and the opticalintensity of the second sensor is greater than the optical intensity ofthe first sensor when the substrate is misaligned.
 10. The method ofclaim 6, further comprising: providing an alarm to a user when theoptical intensity of one of the first sensor or second sensor is notattenuated by the substrate.
 11. A method for transferring a substratein a processing system, comprising: positioning a substrate on an endeffector in a first chamber; moving the substrate through an openingbetween the first chamber and a second chamber along a substrate travelpath; and sensing opposing sides of the substrate travel path using atleast two sensors positioned proximate to the opening, each of the atleast two sensors defining a beam path that is directed through opposingedge regions of the substrate when at least a portion of an edge regiontraverses the beam path.
 12. The method of claim 11, wherein the firstchamber is a processing chamber and the second chamber is a transferchamber.
 13. The method of claim 12, wherein the at least two sensorsare coupled to the transfer chamber.
 14. The method of claim 11, whereinthe substrate is moved through the opening at a speed of about 100millimeters per second to about 2000 millimeters per second.
 15. Themethod of claim 11, further comprising: detecting at least one edgeregion of the substrate, wherein the beam path impinges a top surface ora bottom surface of the edge region.
 16. The method of claim 15, whereinthe beam path is substantially orthogonal to the top surface or thebottom surface.
 17. The method of claim 15, wherein the beam path isreflected through the top surface or the bottom surface.
 18. The methodof claim 11, further comprising: monitoring an optical intensity fromeach sensor to determine an attenuation of the beam path.
 19. The methodof claim 18, further comprising: providing an alarm to a user when theoptical intensity of the beam path is not attenuated by the substrate.20. A method for transferring a substrate in a processing system,comprising: positioning a substrate on an end effector in a transferchamber; moving the substrate through an opening in the transfer chamberalong a substrate travel path; sensing opposing sides of the substratetravel path using at least two sensors positioned proximate to theopening, each of the at least two sensors defining a beam path that isdirected through the substrate when the substrate traverses the beampath; and detecting the presence of at least one parallel edge region ofthe substrate as the substrate is moved along the substrate travel path.21. The method of claim 20, wherein the at least two sensors aredisposed in the transfer chamber.
 22. The method of claim 21, whereinthe at least two sensors are coupled to a sidewall of the transferchamber.
 23. The method of claim 20, wherein the beam path impinges atop surface or a bottom surface of the at least one parallel edgeregion.
 24. The method of claim 23, wherein the beam path issubstantially orthogonal to the top surface or the bottom surface. 25.The method of claim 23, wherein the beam path is reflected through thetop surface or the bottom surface.
 26. The method of claim 20, furthercomprising: monitoring an optical intensity from each sensor todetermine an attenuation of the beam path.
 27. The method of claim 26,further comprising: providing a signal when the optical intensity is notattenuated by the substrate to indicate an absence of the at least oneparallel edge region.
 28. A substrate processing system having an endeffector disposed in a first chamber, at least a first sensor and asecond sensor, and a controller configured to perform a process,comprising: moving a substrate on the end effector along a substratetravel path through an opening between the first chamber and a secondchamber; sensing opposing sides of the substrate travel path using thefirst and second sensors, each of the first and second sensors defininga beam path that is directed through opposing edge regions of thesubstrate when at least a portion of an edge region traverses the beampath; and monitoring a signal from each of the first and second sensors.29. The system of claim 28, wherein monitoring the signal comprises:monitoring an optical intensity to determine an attenuation of the beampath.
 30. The method of claim 29, further comprising: providing an alarmto a user when the optical intensity of the first sensor is greater thanthe optical intensity of the second sensor to indicate an absence of thesubstrate proximate to the first sensor.